Spatially-defined macrocyclic compounds useful for drug discovery

ABSTRACT

Novel spatially-defined macrocyclic compounds containing specific conformational control elements are disclosed. Libraries of these macrocycles are then used to select one or more macrocycle species that exhibit a specific interaction with a particular biological target. In particular, compounds according to the invention are disclosed as agonists or antagonists of a mammalian motilin receptor and a mammalian ghrelin receptor.

FIELD OF THE INVENTION

This invention relates to spatially-defined macrocyclic compounds withspecific conformational control elements. It also relates to thegeneration of libraries of these macrocycles. These libraries are thenused to select one or more macrocycle species that exhibit a specificinteraction with a particular biological target.

BACKGROUND OF THE INVENTION

Among the variety of compounds that have consistently been found topossess potent and selective biological activity are natural productsand peptides. Indeed, members of these classes have become usefulpharmaceutical agents. Unfortunately, each type has limitations thathave restricted the wider utility of these structures.

In fact, natural products often have extremely complex structures thatare difficult to synthesize, particularly in the combinatorial fashionthat would provide access to a greater number of analogues with which todefine pharmacophoric elements and best explore modulation of thebiological properties of the parent compound. Nevertheless, some effortshave been successful at constructing natural product librariescontaining a modest number of analogues.

Peptides, on the other hand, have been at the forefront of thedevelopment of combinatorial chemistry due to their ease of synthesis onsolid support, the reproducible and high-yielding reactions involved,and the ready availability of starting materials. Peptides being theendogenous ligands for a number of enzymes and receptors, theirmodification can be performed to develop even more potent agonists orinhibitors of these same receptors and enzymes. In addition,combinatorial peptide libraries have been used to find a number ofpreviously unknown active sequences for a wide array of enzyme andreceptor systems.

However, peptidic compounds are plagued by the usual limitationsassociated with the direct use of peptides as pharmaceuticals, includingrapid metabolic degradation by proteases, short pharmacokinetichalf-life, difficulty in transport to site of action in tissues andorgans, poor oral bioavailability and solubility, potentialantigenicity, as well as high manufacturing costs.

Nevertheless, the densely functionalized and structurally diverse natureof peptides is advantageous when seeking new drug molecules. Hence,peptides are primarily used as the starting point or template for thedevelopment of new pharmaceutical leads that often results in structuresthat only partially resemble, if at all, the initial active peptide. Inparticular, the recognition potential of the amino acid side chains hasresulted in attempts to incorporate these side chains into non-peptidicrigid scaffolds that attempt to duplicate the conformational displayrequired for optimal interaction between the molecule and the target, aswell as mimic standard protein and peptide secondary structuralelements. For example, sugars and aromatic rings have been exploited asrigid scaffolds containing amino acids or analogues as pendant moietiesat one or more positions. Compounds and combinatorial librariesutilizing 3- and 4-substituted pyrrolidines as a central template fordisplay of interacting functionality have been disclosed in U.S. Pat.No. 5,646,285 and U.S. Pat. No. 5,891,737.

In another approach, cyclic structures can greatly improve thepharmacological and pharmacokinetic profiles of peptides (MolecularDiversity 2000 (pub. 2002), 5, 289-304). Cyclic peptides analogues offera number of benefits compared with the corresponding linear analogues,including restricted conformational mobility, defined topology, enhancedstability to proteolytic enzymes and modified polarity. Furthermore,cyclic peptides can enhance potency, selectivity, stability,bioavailability and membrane permeability. The stability to enzymaticdegradation of the cyclic structure arises from the difficulty of suchmolecules to attain the extended conformation required to be recognizedas a substrate for peptidases. Very large mixture libraries (10⁸ membersor more) of cyclic peptides have been described in WO 98/54577.

However, larger rings are often too flexible and can occupy too manyconformations to be useful. Further, their molecular size and resultingphysicochemical characteristics do not fit the typical requirements forbeing “drug-like.” Small cyclic peptides containing the key interactingresidues would provide the necessary conformational restriction, but mayhave other disadvantages, including synthetic difficulty, ease ofdimerization, unfavorable ring strain caused by the presence of thepreferred trans amide bonds, lack of stability towards metabolism andhydrolysis to release that strain and limited topological diversity.

Most attention in combinatorial chemistry has been devoted to producingdiversity in terms of chemical composition. However, essentially noeffort has been directed at integrating this with diversity in terms ofthe crucial three-dimensional structure.

The use of certain tether elements to control conformation was reportedin WO 01/25257. However, although those tethers were successful inrestricting the conformational display of the molecule, they only wereable to duplicate a portion of the spatial region accessible to a linearmolecule, which can contain hundreds if not thousands of possibleconformations. To better cover the available conformational space,additional tether elements that define new conformations are required.In addition, the tethers in the previous report were generallyhydrophobic in nature. This effects key properties of the macrocyclicmolecules such as solubility and log P that are known to have an impacton the compound's pharmacological properties, in particular oralbioavailability. Further, variation of these physicochemical propertiesis often required in order to optimize the desired characteristic of amolecule as a therapeutic agent. As well, the early tethers were ratherlimited in their chemical functionality. Since this part of the moleculealso could have interactions with a biological target in addition to itsconformational control function, a greater diversity in the chemicalfunctional groups could prove advantageous. The more chemically diversetethers of the present invention therefore have been designed to addressthese limitations of the existing art and provide the followingbenefits:

-   -   Access to previously inaccessible conformations    -   Modification of physicochemical parameters    -   Improvement of pharmacokinetic profile    -   Additional interacting functionalities for modulation of        biological activity

Growing evidence suggests that molecular rigidity confers favorablepharmacokinetic properties on molecules and leads to improved clinicalsuccess (J. Med. Chem. 2003, 46, 1250-1256; J. Med. Chem. 2002, 45,2615-2623). The tethers of the present invention therefore will beextremely useful in utilizing these macrocyclic molecules in the searchfor new pharmaceuticals. Examples of the activity that have beenexhibited by representative molecules of the invention are provided.

Therefore, there remains a need for specifically designed chemicalentities built on a macrocyclic framework, which exploit thethree-dimensional conformation changes triggered by peptidicmodifications and/or by inserting specific tether-like portions, intheir macrocyclic skeleton.

SUMMARY OF THE INVENTION

The present invention is directed towards spatially-defined macrocycliccompounds which incorporate conformational control elements in order tolimit their three-dimensional structure to a small number of spatialorientations. These compounds are defined by general formula (1):

whereinA₁, A₂, A₃ and A₄ are natural amino acid residues or unnatural aminoacid residues;A₃ and A₄ are optionally present;W is O or —NR₁—, wherein R₁ is selected from the group consisting ofhydrogen, alkyl, substituted alkyl, acyl and sulfonyl;T is a bivalent radical chosen from the group consisting of

wherein q₁, q₂, q₃, q₆, q₇, q₈, q₉, q₁₀, q₁₁, q₁₃, q₁₅ and q₁₆ are eachindependently 1, 2, 3, 4 or 5;q₄ and q₁₈ are independently 1 or 2;q₅ is 2, 3 or 5;q₁₂ and q₁₄ are each independently 0, 1, 2, 3 or 4;q₁₇ is 0, 1, 2 or 3;P₁, P₂, P₃ P₄ and P₅ are each independently O, S or NH;

P₆ is N or CH; P₇ is O or CR₅₂R₅₃;

R₃₆ is hydrogen, C₁-C₆ alkyl, benzyl or acyl;R₅₀ and R₅₁ are independently selected from the group consisting ofhydrogen, alkyl, hydroxy, alkoxy, or amino with the proviso that if oneof R₅₀ or R₅₁ is hydroxy, alkoxy or amino, the other is hydrogen oralkyl;R₅₂ and R₅₃ are independently selected from the group consisting ofhydrogen, alkyl, hydroxy, alkoxy, or amino with the proviso that if oneof R₅₂ or R₅₃ is hydroxyl, alkoxy or amino, the other is hydrogen oralkyl;R₅₄, R₅₅, R₅₆, R₅₇ and R₅₈ are independently selected from the groupconsisting of hydrogen, alkyl, hydroxy, alkoxy, or amino;R_(AA) is a side-chain of a natural amino acid or a side-chain of anunnatural amino acid;(W) indicates the point of attachment of T to W;and (A₁) indicates the point of attachment of T to A₁.

Libraries of these compounds are then used to select one or moremacrocycle species that exhibit a specific interaction with a particularbiological target. Such targets include, but are not limited to, enzymesand receptors. More particularly, the macrocyclic libraries of theinvention serve as a readily accessible source of diverse macrocycliccompounds for use in identifying new biologically active macrocycliccompounds through pharmaceutical candidate screening assays, for use instudies defining structure/activity relationships, and/or for use inclinical investigation.

In particular, compounds of formula (I) are disclosed as agonists orantagonists of a mammalian motilin receptor and a mammalian ghrelinreceptor.

While the invention will be described in conjunction with an exampleembodiment, it will be understood that it is not intended to limit thescope of the invention to such embodiment. On the contrary, it isintended to cover all alternatives, modifications and equivalents as maybe included as defined by the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure (I) is a general scheme showing one approach to the solid phasesynthesis of compounds of the invention.

Figure (II) is a general scheme showing a second approach to the solidphase synthesis of compounds of the invention.

FIGS. 3-19 are synthetic schemes that show routes to specific tethers(T) used for the synthesis of compounds of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The macrocyclic compounds of the present invention incorporate a varietyof tethers, thus allowing coverage of a specific section ofconformational space. Furthermore, these tethers are selected on thebasis of their ability to synthetically produce macrocycles inreasonable yield across a wide range of sequences. Accordingly, thecompounds of the invention, which incorporate these tethers, represent awide variety of different conformations, with some more rigid and othersmore flexible. In addition, some of the tethers are much more rigid intheir conformation, sometimes displaying essentially only one low energyform. In these cases, improved biological results would provideexcellent information on the specific, optimum bioactive conformation.Additionally, in contrast to many traditional approaches, the samesynthetic routes and methods are employed in this optimization process.The ability to rapidly access such information transforms what isusually an extremely difficult and time intensive task into a much morestraight forward undertaking.

As such, this invention permits the simultaneous investigation ofchemical and conformational diversity within a single structuralframework and therefore possesses great potential for use in increasingthe speed and efficiency of research aimed at new pharmaceuticals.

Accordingly, the invention provides macrocyclic compounds of formula (I)wherein A₁, A₂, A₃, A₄, W and T are as defined previously.

in a specific embodiment, there are provided compounds of formula (I), Tis chosen from the following bivalent radicals:

wherein Y is selected from hydrogen, alkyl, benzyl or acyl.

The invention also provides compounds of formula 1 wherein at least oneof A₁, A₂, A₃ and A₄ can further be a protected natural or unnaturalamino acid residue.

The present invention has applicability to a broad range of biologicaltargets that likewise represent diverse therapeutic indications. Activecompounds initially generated can be further optimized and refined toeventually provide lead clinical candidates. A further advantage of theinvention is that these subsequent steps in the optimization process canbe conducted utilizing the same basic chemical synthesis pathway, hencegreatly simplifying and speeding up what is typically an extremelytime-consuming phase of the overall drug discovery process.

In particular, the invention provides compounds of formula (I)) whichare agonists or antagonists of a mammalian motilin receptor and/or amammalian ghrelin receptor.

Motilin, a linear 22-amino acid peptide, plays a critical regulatoryrole in the GI physiological system through governing of fastinggastrointestinal motor activity. As such, the peptide is periodicallyreleased from the duodenal mucosa during fasting in mammals, includinghumans. More precisely, motilin exerts a powerful effect on gastricmotility through the contraction of gastrointestinal smooth muscle tostimulate gastric emptying, decrease intestinal transit time andinitiate phase III of the migrating motor complex in the small bowel.Due to the critical and direct involvement of motilin in control ofgastric motility, agents that either diminish (hypomotility) or enhance(hypermotility) the activity at the motilin receptor, are a particularlyattractive area for further investigation in the search for neweffective pharmaceuticals towards these indications. Macrocyclicantagonists of the motilin receptor are disclosed in U.S. Prov. Pat.Appl. Ser. No. 60/479,223.

Likewise, ghrelin is a key peptide hormone involved in a number ofimportant physiological functions including growth hormone secretion,maintenance of energy balance, appetite and gut motility. As such,antagonists of this receptor have been investigated for treatment ofobesity, while ghrelin agonists have interest in treatment of a varietyof diseases, including conditions caused by growth hormone deficiency,wasting syndrome, and GI disorders involving dysmotility.

motilin (human, porcine)Phe-Val-Pro-Ile-Phe-Thr-Tyr-Gly-Glu-Leu-Gln-Arg-Met-Gln-Glu-Lys-Glu-Arg-Asn-Lys-Gly-Gln ghrelin (human)Gly-Ser-Ser(Oct)-Phe-Leu-Ser-Pro-Glu-His-Gln-Arg-Val-Gln-Gln-Arg-Lys-Glu-Ser-Lys-Lys-Pro-Pro-Ala- Lys-Leu-Gln-Pro-Arg

EXAMPLES Synthesis Method

An assortment of synthetic strategies, involving both solution and solidphase techniques, can be used to access the macrocyclic compounds of theinvention, several of which have already been disclosed in WO 01/25257.

An outline of a first approach to the solid phase synthesis of thecompounds of the invention, using a thioester linker strategy isprovided in Figure (I). A second approach, called ring-closingmetathesis (RCM), is also generally outlined in figure (II).

In both, the construction involves four phases: first is synthesis ofthe building blocks, comprising mainly recognition elements forinteraction at biological targets, plus the key tether moiety, primarilyfor control and definition of conformation. These building blocks areassembled together, typically in a sequential fashion, in a second phaseemploying standard chemical transformations and those described in theStandard Procedures herein. The precursors from the assembly are thencyclized in the third stage, which could involve multiple steps, toprovide the macrocyclic structures. Finally, a post-cyclizationprocessing stage involving removal of protecting groups and optionalpurification then provides the desired final compounds.

General Information

Reagents and solvents were of reagent quality or better and were used asobtained from various commercial suppliers unless otherwise noted. DMF,DCM, DME and THF used are of DriSolv® (EM Science, E. Merck) orsynthesis grade quality except for (i) deprotection, (ii) resin cappingreactions and (iii) washing. NMP used for the amino acid (AA) couplingreactions is of analytical grade. DMF was adequately degassed by placingunder vacuum for a minimum of 30 min prior to use. Boc- andFmoc-protected amino acids and side chain protected derivatives,including those of N-methyl and unnatural amino acids, were obtainedfrom commercial suppliers or synthesized through standard methodologiesknown to those in the art. Ddz-amino acids were either synthesized bystandard methods, or obtained commercially from Orpegen (Heidelberg,Germany) or Advanced ChemTech (Louisville, Ky., USA). Bts-amino acidswere synthesized by established procedures. Hydroxy acids were obtainedfrom commercial suppliers or synthesized from the corresponding aminoacids as described in the literature (Tetrahedron 1989, 45, 1639-1646;Tetrahedron 1990, 46, 6623-6632; J. Org. Chem. 1992, 57, 6239-6256.; J.Am. Chem. Soc. 1999, 121, 6197-6205). Analytical TLC was performed onpre-coated plates of silica gel 60F254 (0.25 mm thickness) containing afluorescent indicator.

¹H and ¹³C NMR spectra were recorded on a Varian Mercury 300 MHzspectrometer and are referenced internally with respect to the residualproton signals of the solvent. Information about the conformation of themolecules in solution can be determined utilizing appropriatetwo-dimensional NMR techniques known to those skilled in the art.

HPLC analyses are performed on a Waters Alliance system 2695 running at1 mL/min using an Xterra MS C18 column (or comparable) 4.6×50 mm (3.5□m). A Waters 996 PDA provided UV data for purity assessment. AnLCPackings splitter (50:40:10) allowed the flow to be separated in threeparts. The first part (50%) went to a mass spectrometer (MicromassPlatform II MS equipped with an APCI probe) for identity confirmation.The second part (40%) went to an evaporative light scattering detector(ELSD, Polymer Laboratories, PL-ELS-1000) for purity assessment and thelast portion (10%) to a chemiluminescence nitrogen detector (CLND, AntekModel 8060) for quantitation and purity assessment. Data was capturedand processed utilizing the most recent version of the Waters Millenniumsoftware package.

Preparative HPLC purifications were performed on final deprotectedmacrocycles using the Waters FractionLynx system, on an XTerra MS C18column (or comparable) 19×100 mm (5 □m). The injections were done usingan At-Column-Dilution configuration with a Waters 2767injector/collector and a Waters 515 pump running at 2 mL/min. The massspectrometer, HPLC, and mass-directed fraction collection are controlledvia MassLynx software version 3.5 with FractionLynx. Fractions (13×125mm tubes) shown by MS analysis to contain the product were evaporatedunder reduced pressure, most typically on a centrifugal evaporatorsystem (Genevac HT-4, ThermoSavant Discovery, SpeedVac or comparable)or, alternatively, lyophilized. Compounds were then thoroughly analyzedby LC-MS-UV-ELSD-CLND analysis for identity confirmation, purity andquantity assessment.

Automated medium pressure chromatographic purifications were performedon an Isco CombiFlash 16× system with disposable silica or C18cartridges that permitted up to sixteen (16) samples to be runsimultaneously. MS spectra were recorded on a Waters Micromass PlatformII or ZQ system. HRMS spectra were recorded with a VG Micromass ZAB-ZFspectrometer. Chemical and biological information were stored andanalyzed utilizing the ActivityBase database software (IDBS, Guildford,Surrey, UK).

The term “concentrated/evaporated/removed under reduced pressure”indicates evaporation utilizing a rotary evaporator under either wateraspirator pressure or the stronger vacuum provided by a mechanical oilvacuum pump as appropriate for the solvent being removed. “Dry pack”indicates chromatography on silica gel that has not been pre-treatedwith solvent, generally applied on larger scales for purifications wherea large difference in R_(f) exists between the desired product and anyimpurities. “Flash chromatography” refers to the method described assuch in the literature and is applied to chromatography on silica gel(230-400 mesh, EM Science) used to remove impurities some of which maybe close in R_(f) to the desired material. Methods specific for solidphase chemistry are detailed separately.

General Methods for Solid Phase Chemistry

These methods can be equally well applied for the synthesis of singlecompounds or small numbers of compounds, as well as for the synthesis oflibraries of compounds of the present invention.

For solid phase chemistry, the solvent choice is important not just tosolubilize reactants as in solution chemistry, but also to swell theresin. Certain solvents interact differently with the polymer matrixdepending on its nature and can affect this swelling property. As anexample, polystyrene (with DVB cross-links) swells best in nonpolarsolvents such as DCM and toluene, while shrinking when exposed to polarsolvents like alcohols. In contrast, other resins such as PEG-graftedones like TentaGel, maintain their swelling even in polar solvents. Forthe reactions of the present invention, appropriate choices can be madeby one skilled in the art. In general, polystyrene-DVB resins areemployed with DMF and DCM common solvents. The volume of the reactionsolvent required is generally 1-1.5 mL per 100 mg resin. When the term“appropriate amount of solvent” is used in the synthesis methods, itrefers to this quantity. The recommended quantity of solvent roughlyamounts to a 0.2 M solution of building blocks (linkers, amino acids,hydroxy acids, and tethers, used at 5 eq relative to the initial loadingof the resin). Reaction stoichiometry was determined based upon the“loading” (represents the number of active functional sites, given asmmol/g) of the starting resin.

The reaction can be conducted in any appropriate vessel, for exampleround bottom flask, solid phase reaction vessel equipped with a frittedfilter and stopcock, or Teflon-capped jar. The vessel size should besuch that there is adequate space for the solvent, and that there issufficient room for the resin to be effectively agitated taking intoaccount that certain resins can swell significantly when treated withorganic solvents. The solvent/resin mixture should fill about 60% of thevessel. Take note that all agitations for solid phase chemistry are bestconducted with an orbital shaker (for example Forma Scientific, model430, 160-180 rpm), except for those where scale makes use of gentlemechanical stirring more suitable, to ensure adequate mixing which isgenerally accepted to be important for a successful reaction.

The volume of solvent used for the resin wash is a minimum of the samevolume as used for the reaction, although more is generally used toensure complete removal of excess reagents and other soluble residualby-products. Each of the resin washes specified in the Examples shouldbe performed for a duration of at least 5 min with agitation (unlessotherwise specified) in the order listed. The number of washings isdenoted by “nx” together with the solvent or solution, where n is aninteger. In the case of mixed solvent washing systems, both are listedtogether and denoted solvent 1/solvent 2. The ratio of the solventmixtures DCM/MeOH and THF/MeOH used in the washing steps is (3:1) in allcases. Other mixed solvents are as listed. After washing, drying in the“standard manner” means that the resin is dried first in air (1 h), andsubsequently under vacuum (oil pump usually) until full dryness isattained (minimum 30 min, to O/N).

For representative examples of the new tether moieties disclosed herein,the synthetic routes presented in FIGS. 3-19 are employed withadditional information on selected examples presented further below.Although the routes described represent a specific protection strategy,other suitable protecting groups known in the art can also be employed.

Example T12 Standard Procedure for the Synthesis of Tether T12

For an outline of this route, see FIG. 3. In a 3-L flame-driedthree-neck flask, a solution of (aminomethyl)phenylthiobenzyl alcohol(12-0, 96 g, 0.39 mol) in degassed DMF (1 L, 0.4 M) was prepared. Tothis was added Ddz-N₃ (0.95 eq), followed by TMG (0.39 mol, 49 mL). Thereaction was stirred for 10 min, then DIPEA (68 mL, 0.39 mol) added. Themixture was heated at 50° C. under N₂ until TLC indicated no Ddz-N₃remained (48 h typically). (TLC eluent: EtOAc:Hex 50:50; detection:ninhydrin). Upon completion, to the reaction mixture was added 3 Lcitrate buffer and the separated aqueous layer extracted with Et₂O(3×1500 mL). The combined organic phase was washed sequentially withcitrate buffer (2×200 mL), water (2×200 mL) and brine (2×200 mL). Theorganic layer was dried over MgSO₄, filtered and the filtrate evaporatedunder reduced pressure. A dark orange oil was obtained, which waspurified by dry-pack. For this procedure, the oil was first dissolved inEtOAc:Hex:DCM:TEA (20:80:1:0.5, v/v/v/v). At this point, a little extraDCM was sometimes required to ensure complete dissolution. The solutionwas loaded onto the column, then the column eluted withEtOAc:Hex:DCM:Et₃N (20:80:1:0.5) until all the impurities were separatedout as indicated by TLC, paying particular attention to that closest tothe desired product. The elution was then continued withEtOAc:hexanes:Et₃N 30:70:0.5 (v/v/v) and finally with EtOAc:hexanes:Et₃N(50:50:0.5) to elute the desired product. After removal of the solventfrom the fractions containing the product under reduced pressure, theresidue was dissolved in the minimum amount of DCM, a three-fold largervolume of hexanes added, then the solvents again evaporated underreduced pressure. This treatment was repeated until an off-white foamwas obtained. The latter solidified while drying under vacuum (oilpump). Alternatively, the material yielded a solid after sequentialconcentration with DCM (1×) and hexanes (2×). Tether T12 was obtained asan off-white solid (85-90% yield).

Example T13 Standard Procedure for the Synthesis of Tether T13

Protected versions of tether T13 are accessed through a route (see FIG.4) analogous to that described below in more detail for T14, exceptstarting from H-Ser-OEt.HCl, in an overall yield of 14-30% for the 6step sequence.

¹H NMR (CDCl₃): δ 7.53 (1H, s, RR′C═CH—O), 6.42-6.58 (2H, m, Ph),6.30-6.38 (1H, m, Ph), 5.40-5.50 (1H, m, NH), 4.57 (2H, s, CH ₂OH), 4.40(2H, d, CH ₂NHDdz), 3.78 (6H, s, 2×(CH ₃OPh)), 2.23-2.00 (1H, broad,OH), 1.76 (6H, s, RR′C(CH ₃)₂).

¹³C NMR (CDCl₃): δ 162, 161, 155, 149, 141, 136, 103, 99, 82, 57, 56,39, 29.

Example T14 Standard Procedure for the Synthesis of Tether T14

See FIG. 5 for an outline of the synthetic scheme.

-   Step T14-1: A solution of 4.4 M sodium methoxide in MeOH (1.0 mL,    4.6 mmol, 0.01 eq) in DCM (300 mL) at 0° C. was diluted with MeOH    (35 mL). Dichloroacetonitrile (50 g, 455 mmol, 1.0 eq) was added    over 45 min and the resulting mixture stirred at 0° C. for 1 h.    L-Cysteine ethyl ester hydrochloride (84.5 g, 455 mmol, 1.0 eq) was    added and the reaction stirred O/N at rt. The reaction mixture was    diluted with DCM and water. The separated aqueous phase was    extracted with DCM (2×). The combined organic phase was dried over    MgSO₄, filtered and the filtrate concentrated under reduced    pressure. The crude product obtained was acceptable for use in the    next step without further purification.-   Step T14-2: To a solution of the crude product from step T14-1 (455    mmol based on the theoretical yield) in DCM (500 mL) was added DIPEA    (119 mL, 652.5 mmol, 1.5 eq). The resulting mixture was stirred at    50° C. for 5 h, then at rt O/N. The reaction was monitored by TLC    (30% EtOAc: 70% Hex; detection: UV and CMA, R_(f)=0.29). Upon    completion, the reaction mixture was diluted with DCM and water. The    separated aqueous phase was extracted with DCM (2×). The combined    organic phase was dried over MgSO₄, filtered and the filtrate    concentrated under reduced pressure. ¹H NMR was used to verify the    purity and identity of the intermediate compound. The crude product    obtained was acceptable for use in the next step without further    purification (yield: 100%).-   Step T14-3: To a solution of the crude product from step T14-2 (77    g, 375 mmol, 1.0 eq) in DMF (500 mL) was added sodium azide (122 g,    1874 mmol, 5.0 eq). The resulting mixture was mechanically stirred    at 65° C. O/N. The reaction was monitored by ¹H NMR because the    starting material and product co-eluted on TLC. After completion and    cooling to rt, the reaction mixture was diluted with Et₂O and an    aqueous solution of saturated NH₄Cl. The separated aqueous phase was    extracted with Et₂O (2×). The combined organic phase was washed with    brine, dried over MgSO₄, filtered and the filtrate concentrated    under reduced pressure. ¹H NMR was used to verify the purity and    identity of the intermediate compound. The crude product obtained    was acceptable for use in the next step without further purification    (yield: 93%).-   Step T14-4: To a solution of the crude azide from step T14-3 (73.1    g, 345 mmol, 1.0 eq) in 95% EtOH (700 mL) was added 10% Pd/C (18.3    g, 17.3 mmol, 0.05 eq). Hydrogen gas was bubbled into the suspension    for 1 h, then the resulting mixture stirred O/N with a balloon of    hydrogen. The reaction was monitored by TLC (30% EtOAc: 70% Hex;    detection: UV and ninhydrin.). The final product remained at the    baseline and was positive to ninhydrin. If the reaction was not    complete as indicated by TLC, another portion of 10% Pd/C (25% of    that originally used) was added, hydrogen bubbled through the    solution and the resulting suspension was stirred at rt again O/N.    The reaction solution was filtered through a Celite pad and the pad    rinsed thoroughly with EtOAc (until no further product was being    recovered as indicated by TLC). ¹H NMR was used to verify the purity    and identity of the intermediate compound. The crude product    obtained was acceptable for use in the next step without further    purification (yield: 93%).-   Step T14-5: To a solution of the crude amine from step T14-4 (59.5    g, 320 mmol, 1.0 eq) in degassed (maintained on vacuum pump for 1 h)    DMF (200 mL) were sequentially added Ddz-N₃ (93.3 g, 352 mmol, 1.1    eq), TMG (40.1 mL, 320 mmol, 1.0 eq) and DIPEA (55.8 mL, 320 mmol,    1.0 eq). The resulting solution was stirred at rt for 2 d. The    reaction was monitored by TLC (100% EtOAc; detection: UV and    ninhydrin, R_(f)=0.52). Upon completion, the reaction mixture was    diluted with Et₂O and an aqueous solution of citrate buffer (1 M).    The separated aqueous phase was extracted with Et₂O (2×). The    combined organic phase was washed with citrate buffer (1 M, 2×),    water (2×), and brine (2×), then dried over MgSO₄, filtered and the    filtrate concentrated under reduced pressure. The crude product was    purified by dry-pack (20% EtOAc: 80% Hex to 50% EtOAc: 50% Hex) to    give the protected amino ester as a yellow solid. ¹H NMR was used to    verify the identity of the intermediate compound (yield: 65%).-   Step T14-6: To a solution of the protected amino ester from step    T14-5 (10.5 g, 25.7 mmol, 1.0 eq) in THF (150 mL) at 0° C. were    added lithium borohydride (1.68 g, 77.1 mmol, 3.0 eq) and MeOH (3.1    mL, 77.1 mmol, 3.0 eq). The resulting mixture was stirred for 1 h,    then identical portions of lithium borohydride and MeOH were added.    The resulting mixture was stirred at rt for 3 h. The reaction was    monitored by TLC (5% MeOH, 95% EtOAc; detection: UV and ninhydrin,    R_(f)=0.27. Note that the boronate co-eluted with the starting    material, but after quenching, this spot disappeared). The reaction    mixture was cooled to 0° C. and water was added very slowly (100-150    mL) to quench the reaction. On larger scales, the salts generated in    the reaction were not completely soluble in the aqueous phase at    this stage which complicated the extraction and led to lower yields.    The resulting mixture was then stirred O/N. The aqueous phase was    extracted with EtOAc (4×). The organic phase was dried over MgSO₄,    filtered and the filtrate concentrated under reduced pressure. The    compound was purified by flash chromatography (3% MeOH, 97% EtOAc)    to give tether Ddz-T14 as a pale yellow solid (yield: 67%).

¹H NMR (CDCl₃, ppm): 7.53 (1H, s, RR′C═CH—S), 6.42-6.58 (2H, m, Ph),6.35 (1H, t, Ph), 5.60-5.50 (1H, m, NH), 4.75 (2H, s, CH ₂OH), 4.60 (2H,d, CH ₂NHDdz), 3.78 (6H, s, 2×(CH ₃OPh)), 2.70-2.50 (1H, broad, OH),1.76 (6H, s, RR′C(CH ₃)₂).

¹³C NMR (CDCl₃, ppm): 170, 161, 157, 156, 149, 116, 103, 99, 82, 61, 56,42, 29.

Example T21 Standard Procedure for the Synthesis of Tether T21

See FIG. 6 for an outline of the synthetic scheme that provides themulti-step protocol for this tether containing methyl ether protectionfor its secondary hydroxyl groups. Alternative protection that is easierto remove, such as the acetonide, is also possible via this route.

Example T22 Standard Procedure for the Synthesis of Tether T22

An outline of the synthetic scheme that provides efficient routes to thediastereomeric forms of this tether is shown in FIG. 7.

Example T23 Standard Procedure for the Synthesis of Tether T23

The synthetic scheme that provides routes to this tether in shown isFIG. 8. Modifications can be used for homologous tethers.

Example T24 Standard Procedure for the Synthesis of Tether T24

The synthetic approach to this tether is shown in FIG. 9.

Example T24 Standard Procedure for the Synthesis of Tether T26

The synthetic scheme that provides this tether is shown in FIG. 10.

MW Calc. for C₁₈H₂₅NO₆, 351.39; MS found (M+H)⁺ 352

Example T27 Standard Procedure for the Synthesis of Tether T27

An outline of the synthetic scheme is shown in FIG. 11.

Step T27-1: Ddz-N-(6-O-TBDPS, 2,3-deoxy-β-D-ribofuranosyl)methylamine(27-1). To a solution of 26-5 (20 g, 0.03 mmol) in EtOAc (40 mL) wasadded 10% rhodium on alumina (200 mg). The mixture was hydrogenatedunder atmospheric pressure using balloon of H₂ gas. (CAUTION! Hydrogengas is flammable.) After 12 h, the reaction mixture was filtered througha short pad of Celite and the filter cake washed with MeOH. The reactionhad to be monitored by NMR since the starting material and product hadthe same R_(f) on TLC. The filtrate and washings were combined andconcentrated under reduced pressure. The residue was azeotroped with drytoluene to afford a 98% yield of 27-1, which was used directly in thenext step without further purification. MW Calc. for C₃₄H₄₅NO₆Si,591.8097; MS found (M+H)⁺ 592.

Step T27-2: Ddz-N-(2,3-deoxy-β-D-ribofuranosyl)methylamine (Ddz-T27).The crude product, 27-1, from the previous step (100 g, 0.17 mol) wasdissolved in anhydrous THF (500 mL). To the resulting clear solution wasadded TBAF (0.25 mol, 250 mL) and the reaction stirred for 2 h at rt.The reaction was monitored by TLC [(EtOAc/hexanes, 1:1) detection:ninhydrin, R_(f)=0.5]. When the reaction was complete, the solution waspoured into ice water and the aqueous solution was extracted with DCM(3×400 mL). The combined organic extract was washed with saturatedcitrate buffer (1×300 mL), H₂O (200 mL) and brine (200 mL). The washedorganic extract was dried over anhydrous Na₂SO₄, filtered and evaporatedunder reduced pressure to give an oily residue. This residue waspurified by flash chromatography (EtOAc/hexanes, 1:1, R_(f)=0.5) to givethe protected tether (Ddz-T27) as a syrup (yield 90%). δ

¹H NMR (CDCl₃, 300 MHz): δ 1.61 (m, 1H), 1.74 (s, 6H); 1.80-1.88 (m,3H); 2.66 (s_(b), 1H); 3.21 (m, 2H); 3.26 (m, 1H), 3.67 (m, 1H); 3.75(s, 6H); 4.05 (m, 2H); 5.25 (m, 1H); 6.32 (m, 1H); 6.51 (m, 2H).

HPLC (Standard Gradient): Retention time (t_(r)): 6.43 min

MW Calc. for C₁₈H₂₇NO₆, 353.4101; MS found (M+H)⁺ 354.

Example T33 Standard Procedure for the Synthesis of Tether T33

An outline of the synthetic scheme towards this chiral tether is shownin FIG. 12. The enantiomers are accessed depending on the configurationof the starting lactic acid derivative with the (R)-isomer coming from(S)-methyl lactate and the (S)-isomer of T33 resulting from (R)-methyllactate

¹H NMR (CDCl₃): δ 7.18-7.11 (m, 2H), 6.90 (m, 2H), 6.52 (m, 2H), 6.33(m, 1H), 5.09 (bt, 1H), 4.52 (m, 1H), 3.77 (s, 6H), 3.08 (bq, 2H), 2.64(bt, 2H), 1.75 (m, 8H); 1.27 (bd, 3H)

¹³C NMR (CDCl₃): δ 160.8, 155.5, 149.5, 131.2, 130.6, 127.4, 121.2,113.3, 103.2, 98.4, 80.7, 74.8, 66.5, 55.4, 40.2, 30.6, 29.3, 29.2,27.4, 16.1

Example T38 Standard Procedure for the Synthesis of Tether T38

An outline of the synthetic scheme for racemic material is shown in FIG.13. The enantiomers are accessed through the use of the optically purepropylene oxide enantiomers. Since the center of the epoxide is invertedduring the protocol, the (R)-epoxide provides T38(S), while the(S)-epoxide provides T38(R).

¹H NMR (CDCl₃): δ 7.20-7.10, (m, 2H), 6.95-9.80 (m, 2H), 6.55 (bs, 2H),6.35 (s, 1H), 5.18 (bt, 1H), 4.12 (m, 1H), 3.98 (m, 2H), 3.80 (s, 6H),3.15 (bq, 2H), 2.65 (t, 2H), 1.98 (bs, 2H), 1.65 (bs, 6H), 1.25 (m, 3H).

Example T39 Standard Procedure for the Synthesis of Tether T39

See FIG. 14 for an outline of the synthetic scheme for racemic product.Enantiomeric versions can be accessed via resolution methodologies oruse of an asymmetric Michael addition in the third step.

¹H NMR (CDCl₃): δ 7.11-7.08 (2H, m), 6.86 (1H, t), 6.76 (1H, d), 5.05(1H, broad), 4.26-3.85 (4H, m), 3.22-3.07 (2H, m), 2.71 (1H, broad),1.66-1.60 (2H, m), 1.33 (9H, s), 1.17 (3H, d).

¹³C NMR (CDCl₃): δ 156.1, 135.0, 127.1, 127.0, 121.4, 111.7, 69.9, 61.5,39.8, 38.4, 28.7, 20.7.

Example T40 Standard Procedure for the Synthesis of Tether T40

An outline of the synthetic scheme for racemic material is shown in FIG.15, while FIG. 16 outlines the route to both enantiomers involving anenzymatic resolution as the key step.

¹H NMR (CDCl₃): δ7.11-7.08 (2H, m), 6.86 (1H, t), 6.76 (1H, d), 5.05(1H, broad), 4.26-3.85 (4H, m), 3.22-3.07 (2H, m), 2.71 (1H, broad),1.66-1.60 (2H, m), 1.33 (9H, s), 1.17 (3H, d).

¹³C NMR (CDCl₃): δ 156.1, 135.0, 127.1, 127.0, 121.4, 111.7, 69.9, 61.5,39.8, 38.4, 28.7, 20.7.

Example T41 Standard Procedure for the Synthesis of Tether T41

See FIG. 18( a) for an outline of the synthetic scheme that provides anappropriately protected derivative for use in macrocycle constructionvia FIG. 1.

¹H NMR (CDCl₃): δ1.23 (s, 3H), 1.49 (s, 3H), 1.69 (s, 3H), 1.74 (s, 3H),1.90 (m, 2H), 2.35 (m, 1H), 3.35 (m, 2H), 3.76 (s, 6H), 3.92 (m, 2H),4.40 (m, 2H), 5.10 (m, 1H), 6.15 (s, 1H), 6.25 (s, 2H).

¹³C NMR (CDCl₃): δ 25.52 (CH₃), 27.53 (CH₃), 28.88 (CH₃), 29.61 (CH₃),35.92 (CH₂), 42.62 (CH₂), 55.43 (CH₃), 60.60 (CH₂), 82.38 (CH), 83.33(CH), 83.68 (CH), 84.96 (CH), 98.26 (CH), 103.23 (CH), 118.3 (Cq),149.50 (Cq), 156.20 (Cq), 160.02 (Cq)

MW Calcd. for C₂₂H₃₃NO₈: 439.50; MS Found: (M+H)⁺ 440

Example T54 Standard Procedure for the Synthesis of Tether T54

See FIG. 18( c) for an outline of the synthetic scheme from a T55derivative.

¹H NMR (CDCl₃): δ1.55 (m, 2H), 1.72 (s, 6H), 1.8-2.01 (m, 4H), 2.75(s_(b), 1H), 3.10 (m, 1H), 3.32 (m, 1H), 3.65 (s, 6H), 3.66 (m, 2H),3.90-4.01 (m, 2H), 5.30 (m, 1H), 6.30 (s, 1H), 6.50 (s, 2H).

¹³C NMR (CDCl₃): δ 28.04 (CH₂), 29.18 (CH₃), 29.34 (CH₃), 31.69 (CH₂),38.08 (CH₂), 44.94 (CH₂), 55.41 (CH₃), 61.28 (CH₂), 78.84 (CH), 79.41(CH), 80.75 (Cq), 98.44 (CH), 103.15 (CH), 149.44 (Cq), 155.64 (Cq),160.81 (Cq).

MW Calcd. for C₁₉H₂₉NO₆: 367.44; MS Found: (M+H)⁺ 368

Example T55 Standard Procedure for the Synthesis of Tether T55

See FIG. 18( b) for an outline of the synthetic scheme.

¹H NMR (CDCl₃): δ 1.66 (s, 3H), 1.71 (s, 3H), 1.82 (m, 1H), 1.89 (m,1H), 3.26 (m, 2H), 3.77 (s, 6H), 3.80 (m, 2H), 4.84 (m, 1H), 4.95 (m,1H), 5.20 (m, 1H), 5.70 (m, 1H), 5.85 (m, 1H), 6.32 (s, 1H), 6.49 (s,2H).

¹³C NMR (CDCl₃): δ 29.06 (CH₃), 29.42 (CH₃), 38.73 (CH₂), 44.87 (CH₂),55.45 (CH₃), 61.01 (CH₂), 80.77 (Cq), 85.84 (CH), 86.25 (CH), 98.28(CH), 103.28 (CH), 127.84 (CH), 131.95 (CH), 149.42 (Cq), 155.59 (Cq),160.79 (Cq).

MW Calcd. for C₁₉H₂₇NO₆: 365.42; MS Found: (M+H)⁺ 366

Example T56 Standard Procedure for the Synthesis of Precursor (56-1) forTethers T56 and T57

For some of the tether structures, specifically those arising from thering-closing metathesis methodology (RCM, FIG. 2), the tether is notadded as an already assembled unit, but is constructed during themacrocyclization reaction from appropriate precursor pieces. One suchexample 1d shown in FIG. 19 in which 56-1, containing a pendant alkenemoiety, will be subjected to RCM whereby the alkene will join with analkene in another part of the substrate to form the macrocyclic ringand, hence, construct tether T56 (or homologues). Reduction of thedouble bond in macrocycles containing T56 leads to macrocyclescontaining T57. Other tethers that were constructed in this mannerinclude T46, T47, T49, and T51.

Table 1 lists the structural features for 60 preferred embodiments ofcompounds of formula (I).

Table 2 gives the Mass Spectrum analytical data for these compounds.

TABLE 1 Representative Compounds of formula (I) (I)

Cmpd A₁ A₂ A₃ T^(*) 201

T40(S) 202

T40(S) 203

T38(S) 204

T40(R) 205

T40(R) 206

T38(R) 207

T40(S) 208

T38(S) 209

T40 210

T39 211

T40(R) 212

T58 213

T39 214

T40(R) 215

T59(S) 216

T59(R) 217

T38(R) 218

T59(S) 219

T59(R) 220

T33(R) 222

T38 223

T38 224

T41 225

T41 226

T33(S) 227

T33(R) 228

T12 229

T56(Y = H) 230

T57(Y = H) 231

T56(Y = Me) 232

T57(Y = Me) 233

T21(Y = H) 234

T26 235

T12 236

T13 237

T14 238

T12 241

T38 242

T33(R) 243

T33(S) 244

T33(R) 245

T33(S) 246

T39 247

T58 248

T40 249

T21(Y = H) 250

T24 251

T12 252

T27 253

T14 254

T33(R) 255

T33(S) 256

T39 257

T40 258

T58 259

T12 260

T46 261

T47 262

T49 263

T51 264

T51 ^(*)Designation in parentheses indicates the absolute configuration(R or S) of the chiral center on the tether. If no configuration is sodesignated, the center is racemic. Other designations indicate theidentity of a variable substituent.

TABLE 2 Mass Spectral Analyses for Representative Compounds of formula IMolecular Monoisotopic MS Found Cmpd Molecular Formula Weight Mass (M +H)⁺ 201 C31H42N7O4F3 633.7 633 634 202 C31H44N5O4F 569.7 569 570 203C30H42N7O4Cl 600.2 599 600 204 C31H42N7O4F3 633.7 633 634 205C31H44N5O4F 569.7 569 570 206 C30H42N7O4Cl 600.2 599 600 207C32H43N4O4Cl 583.2 582 583 208 C32H43N4O4F 566.7 566 567 209C32H43N4O4Cl 583.2 582 583 210 C31H43N4O4Cl 571.2 570 571 211C32H43N4O4Cl 583.2 582 583 212 C33H45N4O4Cl 597.2 596 597 213C31H43N4O4F 554.7 554 555 214 C32H43N4O4F 566.7 566 567 215 C31H41N4O5Cl585.1 584 585 216 C31H41N4O5Cl 585.1 584 585 217 C32H43N4O4F 566.7 566567 218 C31H41N4O5F 568.7 568 569 219 C31H41N4O5F 568.7 568 569 220C32H43N4O4F 566.7 566 567 222 C32H46N4O5 566.7 566 567 223 C32H43N4O4Cl583.2 582 583 224 C27H39N4O6Cl 551.1 550 551 225 C27H42N4O7 534.6 534535 226 C31H44N4O5 552.7 552 553 227 C31H44N4O5 552.7 552 553 228C30H38N6O3S 562.7 562 563 229 C28H41N3O8 547.6 547 548 230 C28H43N3O8549.7 549 550 231 C30H45N3O8 575.7 575 576 232 C30H47N3O8 577.7 577 578233 C25H38N4O7 506.6 506 507 234 C25H36N4O5 472.6 472 473 235C38H42N4O4S 650.8 650 651 236 C24H33N5O5 471.5 471 472 237 C24H33N5O4S487.6 487 488 238 C33H40N4O4S 588.8 588 589 241 C30H39N4O4F 538.7 588589 242 C31H44N4O4 536.7 536 537 243 C31H44N4O4 536.7 536 537 244C30H39N4O4F 538.7 538 539 245 C30H39N4O4F 538.7 538 539 246 C30H39N4O4F538.7 538 539 247 C31H41N4O4F 552.7 552 553 248 C30H39N4O4F 538.7 538539 249 C24H33N4O6F 492.5 492 493 250 C26H41N4O3F 476.6 476 477 251C31H36N4O3S 544.7 544 545 252 C23H34N4O4 430.5 430 431 253 C22H29N5O3S443.6 443 444 254 C33H45N4O4Cl 597.2 596 597 255 C33H45N4O4Cl 597.2 596597 256 C33H45N4O4Cl 597.2 596 597 257 C33H45N4O4Cl 597.2 596 597 258C34H47N4O4Cl 611.2 611 612 259 C35H42N4O3S 598.8 598 599 260 C23H35N4O3F434.5 434 435 261 C26H39N4O3Cl 491.1 490 491 262 C27H41N4O3Cl 505.1 504505 263 C28H43N4O3Cl 519.1 518 519 264 C29H45N4O3Cl 533.1 532 533Notes 1. Molecular formulas and molecular weights (MW) are calculatedautomatically from the structure via Activity Base software (IDBS,Guildford, Surrey, UK) or, for MW only, from the freeware programMolecular Weight Calculator v. 6.32 2. M + H obtained from LC-MSanalysis 3. All analyses conducted on material after preparativepurification

Biological Evaluation for Compounds of the Invention

The compounds of the present invention were evaluated for their abilityto interact at the human motilin receptor and the human ghrelin receptorutilizing competitive radioligand binding assays as described in MethodB1 and B2, respectively. Further characterization of the interaction canbe performed utilizing the functional assays described in Methods B3 andB4 for the motilin and ghrelin receptors, respectively. All of thesemethods can be conducted, if so desired, in a high throughput manner topermit the simultaneous evaluation of many compounds.

Results for the examination of representative compounds of the presentinvention using Methods B1 and B2 are presented in Table 3.

Example Method B1 Competitive Radioligand Binding Assay (MotilinReceptor) Materials:

-   -   Membranes were prepared from CHO cells stably transfected with        the human motilin receptor and utilized at a quantity of 1.5        μg/assay point. [PerkinElmer™ SignalScreen Product #6110544]    -   [¹²⁵I]-Motilin (PerkinElmer, #NEX-378); final concentration:        0.04-0.06 nM    -   Motilin (Bachem™, #H-4385); final concentration: 1 μM    -   Multiscreen Harvest plates-GF/B (Millipore™, #MAHFB1H60)    -   Deep-well polypropylene titer plate (Beckman Coulter™, #267006)    -   TopSeal-A (PerkinElmer, #6005185)    -   Bottom seal (Millipore, #MATAH0P00)    -   MicroScint-0 (PerkinElmer, #6013611)    -   Binding Buffer: 50 mM Tris-HCl (pH 7.4), 10 mM MgCl₂, 1 mM EDTA,        0.1% BSA

Assay Volumes:

-   -   150 μL of membranes diluted in binding buffer    -   10 μL of compound diluted in binding buffer    -   10 μL of radioligand ([¹²⁵I]-Motilin) diluted in binding buffer

Final Test Concentrations (N=11) for Compounds:

-   -   10, 5, 2, 1, 0.5, 0.2, 0.1, 0.05, 0.02, 0.01, 0.005 μM.

Compound Handling:

Compounds were provided frozen on dry ice at a stock concentration of 10mM diluted in 100% DMSO and stored at −20° C. until the day of testing.On the test day, compounds were allowed to thaw at room temperature andthan diluted in assay buffer according to the desired testconcentrations. Under these conditions, the maximum final DMSOconcentration in the assay was 0.5%.

Assay Protocol:

In deep-well plates, diluted cell membranes (1.5 μg/mL) are combinedwith 10 μL of either binding buffer (total binding, N=5), 1 μM motilin(non-specific binding, N=3) or the appropriate concentration of testcompound. The reaction is initiated by addition of 10 μl of[¹²⁵I]-motilin (final conc. 0.04-0.06 nM) to each well. Plates aresealed with TopSeal-A, vortexed gently and incubated at room temperaturefor 2 hours. The reaction is arrested by filtering samples throughpre-soaked (0.3% polyethyleneimine, 2 h) Multiscreen Harvest platesusing a Tomtec Harvester, washed 9 times with 500 μL of cold 50 mMTris-HCl (pH 7.4), and than plates are air-dried in a fumehood for 30minutes. A bottom seal is applied to the plates prior to the addition of25 μL of MicroScint-0 to each well. Plates are than sealed withTopSeal-A and counted for 30 sec per well on a TopCount MicroplateScintillation and Luminescence Counter (PerkinElmer) where results areexpressed as counts per minute (cpm).

Data are analyzed by GraphPad™ Prism (GraphPad Software, San Diego,Calif.) using a variable slope non-linear regression analysis. K_(i)values were calculated using a K_(d) value of 0.16 nM for [¹²⁵I]-motilin(previously determined during membrane characterization).

$D_{m\; {ax}} = {1 - {\frac{\begin{matrix}{{{test}\mspace{14mu} {concentration}\mspace{14mu} {with}\mspace{14mu} {maximal}\mspace{14mu} {dispacement}}\mspace{14mu} -} \\{{non}\text{-}{specific}\mspace{14mu} {binding}}\end{matrix}}{{{total}\mspace{14mu} {binding}} - {{non}\text{-}{specific}\mspace{14mu} {binding}}} \times 100}}$

where total and non-specific binding represent the cpm obtained in theabsence or presence of 1 μM motilin, respectively.

Example Method B2 Competitive Radioligand Binding Assay (GhrelinReceptor)

The competitive binding assay at the human growth hormone secretagoguereceptor (hGHS-R1a) was carried out analogously to assays described inthe literature. (Bednarek M A et al. (2000), Structure-function studieson the new growth hormone-releasing peptide ghrelin: minimal sequence ofghrelin necessary for activation of growth hormone secretagogue receptor1a; J Med Chem 43:4370-4376. Palucki B L et al. (2001),Spiro(indoline-3,4′-piperidine) growth hormone secretagogues as ghrelinmimetics; Bioorg Med Chem Lett 11:1955-1957.)

Materials

-   -   Membranes (GHS-R/HEK 293) were prepared from HEK-293 cells        stably transfected with the human ghrelin receptor (hGHS-R1a).        These membranes were provided by PerkinElmer BioSignal        (#RBHGHSM, lot#1887) and utilized at a quantity of 0.71 μg/assay        point.    -   [¹²⁵I]-Ghrelin (PerkinElmer, #NEX-388); final concentration:        0.0070-0.0085 nM    -   Ghrelin (Bachem, #H-4864); final concentration: 1 μM    -   Multiscreen Harvest plates-GF/C (Millipore, #MAHFC1H60)    -   Deep-well polypropylene titer plate (Beckman Coulter, #267006)    -   TopSeal-A (PerkinElmer, #6005185)    -   Bottom seal (Millipore, #MATAH0P00)    -   MicroScint-0 (PerkinElmer, #6013611)    -   Binding Buffer: 25 mM Hepes (pH 7.4), 1 mM CaCl₂, 5 mM MgCl₂,        2.5 mM EDTA, 0.4% BSA

Assay Volumes

Competition experiments were performed in a 300 μL filtration assayformat.

-   -   220 μL of membranes diluted in binding buffer    -   40 μL of compound diluted in binding buffer    -   40 μL of radioligand ([¹²⁵I]-Ghrelin) diluted in binding buffer

Final test concentrations (N=1) for compounds of the present invention:

10, 1, 0.5, 0.2, 0.1, 0.05, 0.02, 0.01, 0.005, 0.002, 0.001 μM. CompoundHandling

Compounds were provided frozen on dry ice at a stock concentration of 10mM diluted in 100% DMSO and stored at −80° C. until the day of testing.On the test day, compounds were allowed to thaw at rt overnight and thendiluted in assay buffer according to the desired test concentrations.Under these conditions, the maximal final DMSO concentration in theassay was 0.1%.

Assay Protocol

In deep-well plates, 220 μL of diluted cell membranes (finalconcentration: 0.71 μg/well) were combined with 40 μL of either bindingbuffer (total binding, N=5), 1 μM ghrelin (non-specific binding, N=3) orthe appropriate concentration of test compound (N=2 for each testconcentration). The reaction was initiated by addition of 40 μL of[¹²⁵I]-ghrelin (final conc. 0.0070-0.0085 nM) to each well. Plates weresealed with TopSeal-A, vortexed gently and incubated at rt for 30 min.The reaction was arrested by filtering samples through MultiscreenHarvest plates (pre-soaked in 0.5% polyethyleneimine) using a TomtecHarvester, washed 9 times with 500 μL of cold 50 mM Tris-HCl (pH 7.4, 4°C.), and then plates were air-dried in a fumehood for 30 min. A bottomseal was applied to the plates prior to the addition of 25 μL ofMicroScint-0 to each well. Plates were than sealed with TopSeal-A andcounted for 30 sec per well on a TopCount Microplate Scintillation andLuminescence Counter (PerkinElmer) using a count delay of 60 sec.Results were expressed as counts per minute (cpm).

Data were analyzed by GraphPad Prism (GraphPad Software, San Diego,Calif.) using a variable slope non-linear regression analysis. K_(i)values were calculated using a K_(d) value of 0.01 nM for [¹²⁵I]-ghrelin(previously determined during membrane characterization).

D_(max) values were calculated using the following formula:

$D_{m\; {ax}} = {1 - {\frac{\begin{matrix}{{{test}\mspace{14mu} {concentration}\mspace{14mu} {with}\mspace{14mu} {maximal}\mspace{14mu} {dispacement}}\mspace{14mu} -} \\{{non}\text{-}{specific}\mspace{14mu} {binding}}\end{matrix}}{{{total}\mspace{14mu} {binding}} - {{non}\text{-}{specific}\mspace{14mu} {binding}}} \times 100}}$

where total and non-specific binding represent the cpm obtained in theabsence or presence of 1 μM ghrelin, respectively.

Example Method B3 Aequorin Functional Assay (Motilin Receptor)Materials:

-   -   Membranes were prepared using AequoScreen™ (EUROSCREEN, Belgium)        cell lines expressing the human motilin receptor (cell line        ES-380-A; receptor accession #AF034632). This cell line is        constructed by transfection of the human motilin receptor into        CHO-K1 cells co-expressing G_(α16) and the mitochondrially        targeted Aequorin (Ref #ES-WT-A5).    -   Motilin (Bachem, #H-4385)    -   Assay buffer: DMEM-F12 (Dulbeccoe's Modified Eagles Medium) with        15 mM HEPES and 0.1% BSA (pH 7.0)    -   Coelenterazine (Molecular Probes™, Leiden, The Netherlands)

Final Test Concentrations (N=5) for Compounds:

-   -   10, 3.16, 1, 0.316, 0.1 μM.

Compound Handling:

Compounds were provided as dry films at a quantity of approximately 1.2mmol in pre-formatted 96-well plates. Compounds were dissolved in 100%DMSO at a concentration of 10 mM and stored at −20° C. until furtheruse. Daughter plates were prepared at a concentration of 500 μM in 30%DMSO with 0.1% BSA and stored at −20° C. until testing. On the test day,compounds were allowed to thaw at room temperature and than diluted inassay buffer according to the desired test concentrations. Under theseconditions, the maximum final DMSO concentration in the assay was 0.6%.

Cell Preparation:

Cells are collected from culture plates with Ca²⁺ and Mg²⁺-freephosphate buffered saline (PBS) supplemented with 5 mM EDTA, pelletedfor 2 minutes at 1000×g, resuspended in assay buffer (see above) at adensity of 5×10⁶ cells/mL and incubated overnight in the presence of 5μM coelenterazine. After loading, cells were diluted with assay bufferto a concentration of 5×10⁵ cells/mL.

Assay Protocol:

For agonist testing, 50 μl of the cell suspension was mixed with 50 μlof the appropriate concentration of test compound or motilin (referenceagonist) in 96-well plates (duplicate samples). The emission of lightresulting from receptor activation was recorded using the FunctionalDrug Screening System 6000 ‘FDSS 6000’ (Hamamatsu Photonics K.K.,Japan).

For antagonist testing, an approximate EC80 concentration of motilin(i.e. 0.5 nM; 100 μL) was injected onto the cell suspension containingthe test compounds (duplicate samples) 15-30 minutes after the end ofagonist testing and the consequent emission of light resulting fromreceptor activation was measured as described in the paragraph above.

Results are expressed as Relative Light Units (RLU). Concentrationresponse curves were analyzed using GraphPad Prism (GraphPad Software,San Diego, Calif.) by non-linear regression analysis (sigmoidaldose-response) based on the equation E=E_(max)/(1+EC₅₀/C)n where E isthe measured RLU value at a given agonist concentration (C), E_(max) isthe maximal response, EC₅₀ is the concentration producing 50%stimulation and n is the slope index. For agonist testing, results foreach concentration of test compound were expressed as percent activationrelative to the signal induced by motilin at a concentration equal tothe EC₈₀ (i.e. 0.5 nM). For antagonist testing, results for eachconcentration of test compound were expressed as percent inhibitionrelative to the signal induced by motilin at a concentration equal tothe EC₈₀ (i.e. 0.5 nM).

Example Method B4 Aequorin Functional Assay (Ghrelin Receptor) Materials

-   -   Membranes were prepared using AequoScreen™ (EUROSCREEN, Belgium)        cell lines expressing the human ghrelin receptor (cell line        ES-410-A; receptor accession #60179). This cell line is        constructed by transfection of the human ghrelin receptor into        CHO-K1 cells co-expressing G_(□16) and the mitochondrially        targeted Aequorin (Ref #ES-WT-A5).    -   Ghrelin (reference agonist; Bachem, #H-4864)    -   Assay buffer: DMEM (Dulbecco's Modified Eagles Medium)        containing 0.1% BSA (bovine serum albumin; pH 7.0.    -   Coelenterazine (Molecular Probes, Leiden, The Netherlands)

Final test concentrations (N=8) for compounds of the invention:

10, 1, 0.3, 0.1, 0.03, 0.01, 0.003, 0.001 μM. Compound Handling

Stock solutions of compounds (10 mM in 100% DMSO) were provided frozenon dry ice and stored at −20° C. prior to use. From the stock solution,mother solutions were made at a concentration of 500 μM by 20-folddilution in 26% DMSO. Assay plates were then prepared by appropriatedilution in DMEM medium containing 0.1% BSA. Under these conditions, themaximal final DMSO concentration in the assay was <0.6%.

Cell Preparation

AequoScreen™ cells were collected from culture plates with Ca²⁺ andMg²⁺-free phosphate buffered saline (PBS) supplemented with 5 mM EDTA,pelleted for 2 min at 1000× g, re-suspended in DMEM—Ham's F12 containing0.1% BSA at a density of 5×10⁶ cells/mL, and incubated overnight at rtin the presence of 5 μM coelenterazine. After loading, cells werediluted with assay buffer to a concentration of 5×10⁵ cells/mL.

Assay Protocol

For agonist testing, 50 μL of the cell suspension was mixed with 50 μLof the appropriate concentration of test compound or ghrelin (referenceagonist) in 96-well plates (duplicate samples). Ghrelin (referenceagonist) was tested at several concentrations concurrently with the testcompounds in order to validate the experiment. The emission of lightresulting from receptor activation in response to ghrelin or testcompounds was recorded using the Hamamatsu FDSS 6000 reader (HamamatsuPhotonics K.K., Japan).

Analysis and Expression of Results

Results were expressed as Relative Light Units (RLU). Concentrationresponse curves were analyzed using GraphPad Prism (GraphPad Software,San Diego, Calif.) by non-linear regression analysis (sigmoidaldose-response) based on the equation E=E_(max)/(1+EC₅₀/C)n where E wasthe measured RLU value at a given agonist concentration (C), E_(max) wasthe maximal response, EC₅₀ was the concentration producing 50%stimulation and n was the slope index. For agonist testing, results foreach concentration of test compound are expressed as percent activationrelative to the signal induced by ghrelin at a concentration equal tothe EC₈₀ (i.e. 3.7 nM). EC₅₀, Hill slope and % E_(max) values arereported.

TABLE 3 Biological Activity of Representative Compounds of formula IBinding Affinity [K_(i) Compound (μM)]¹ Receptor² 201 A motilin (human)202 A motilin (human) 203 A motilin (human) 204 A motilin (human) 205 Bmotilin (human) 206 B motilin (human) 207 A motilin (human) 208 Amotilin (human) 209 A motilin (human) 210 A motilin (human) 211 Amotilin (human) 212 A motilin (human) 213 A motilin (human) 214 Amotilin (human) 215 A motilin (human) 216 A motilin (human) 217 Bmotilin (human) 218 B motilin (human) 219 B motilin (human) 220 Bmotilin (human) 221 B motilin (human) 222 A motilin (human) 223 Amotilin (human) 224 B motilin (human) 226 B motilin (human) 227 Bmotilin (human) 228 B motilin (human) 235 C motilin (human) 236 Bmotilin (human) 237 B motilin (human) 241 A ghrelin (human) 242 Aghrelin (human) 243 A ghrelin (human) 244 A ghrelin (human) 245 Aghrelin (human) 246 B ghrelin (human) 247 B ghrelin (human) 248 Bghrelin (human) 251 B ghrelin (human) 254 A ghrelin (human) 255 Aghrelin (human) 256 B ghrelin (human) 257 A ghrelin (human) 258 Bghrelin (human) 259 C ghrelin (human) 260 C ghrelin (human) 261 Cghrelin (human) 262 B ghrelin (human) 263 B ghrelin (human) 264 Bghrelin (human) ¹Activity presented indicated in the following ranges: A= 0.001-0.10 μM, B = 0.1-1.0 μM, C = 1.0-10.0 μM ²Binding conductedusing the Standard Methods described in the Examples

Although preferred embodiments of the present invention have beendescribed in detail herein, it is to be understood that the invention isnot limited to these precise embodiments and that various changes andmodifications may be effected therein without departing from the scopeor spirit of the present invention.

1-10. (canceled)
 11. A compound of formula W-T-X, wherein W and X areindependently selected from the group consisting of —OH, —NH₂ and —NHR₃,where R₃ is lower alkyl, and T is selected from the group consisting of

wherein Y is hydrogen, alkyl, benzyl or acyl; (W) indicates the point ofattachment of T to W; and (X) indicates the point of attachment of T toX.
 12. The compound of claim 11 further comprising one or moreprotecting groups.
 13. The compound of claim 11, wherein T is thefollowing:

wherein (W) indicates the point of attachment of T to W; and (X)indicates the point of attachment of T to X.
 14. The compound of claim11, wherein T is the following:

wherein (W) indicates the point of attachment of T to W; and (X)indicates the point of attachment of T to X.